Master thesis : Modeling and dynamical analysis of dopaminergic neuron activity and its role in reward quantification

Abstract

Dopamine is a chemical released by the brain which has long been associated with the pleasant feeling that accompanies a reward. The neurons that release such chemical, called dopaminergic neurons, have therefore been the subject of research and study for years. In fact, understanding the behaviour of the neurons that drive the regulation of dopamine levels and their interactions with the other entities that compose the brain is necessary for the understanding of a larger entity called the reward circuit. This circuitry which drives multiple phenomenona such as motivation, emotions, etc. Impairment and alterations in the circuitry is also known to lead to psychiatric disorders and addiction.

Dopaminergic neurons present a specific behaviour as they actually fire in different modes which are imbricated together. On one hand, when unsolicited, they fire at a slow and robust rate. On the other hand, when they are triggered, their frequency of firing increases which also increases the dopamine release. This variability allows to regulate the dopamine in the brain.

This thesis focuses on the study of a model developed by G. Drion on the dynamics of dopaminergic activity.

The first part of this thesis aims to reproduce experimental results that were obtained to validate the model. Using engineering tools such as model reduction and phase plane analysis, a deeper study of the dynamics of the model is performed in order to understand the mechanisms that drive the behaviour of the model.

As a second part, the aim is to use the model in order to develop a hypothesis on the regulation of the firing frequency of dopaminergic neurons according to physiological properties of the neurons and linking it to the quantification of reward in the brain.